1. Field of the Invention
The present invention generally relates to an operation amplifier, and more particularly, to a circuit for providing dynamic current capable of advancing internal slew rate of an operation amplifier.
2. Description of Related Art
Most of analog circuits usually adopts voltage mode to process signals, wherein an operation amplifier (op-amp) in voltage mode is popular and favored by electrical circuit designers due to the low price and stability of electrical behavior. However, a conventional op-amp in voltage mode is limited by the constant gain bandwidth product (GBP) thereof and an insufficient transient response speed, which are limited an electrical circuit designer to deal with a high frequency signal case. In order to get rid of the above-mentioned limitation as dealing with a high frequency signal case, the electrical circuit designer would increase internal slew rate of an operation amplifier for the improving.
It is well known that the internal slew rate of an op-amp depends on the ratio IB/CM of bias current IB of an op-amp over the internal compensation capacitance CM thereof. Thus, in order to advance internal slew rate of a conventional op-amp under the condition of a fixed internal compensation capacitance, the bias current of the op-amp input stage needs to be increased, however, it would make the pole/zero point and the GBP position drifted and accordingly deteriorate the stability of the op-amp. In addition, by increasing the bias current of the op-amp input stage to break through the limitation in case of dealing with a high frequency signal, the power consumption of the op-amp would accordingly increased as the op-amp is in the steady state.